This Phase I application is being submitted with the main objective to develop a highly sensitive and specific imaging method for prostate cancer that is based on a bispecific antibody (bsMAb) pretargeting procedure. The key features of this imaging system is the use of a unique recombinant, humanized tri-Fab bsMAb with divalent binding to the tumor-associated antigen, TROP-2, and another monovalent-binding Fab reactive with the novel hapten, HSG (histamine- succinyl-glycine). It will be used in combination with a small molecular weight hapten-peptide (HP) that will be radiolabeled with 18F based on a new, rapid method for labeling peptides invented by Immunomedics scientists. This pretargeting method has already been shown to be highly sensitive and more specific in targeting cancer than 18F-FDG. Immunohistology studies have shown TROP-2 is widely expressed in all forms of prostate cancer, primary and metastatic, and thus we plan to develop the bsMAb known as TF12 for detecting prostate cancer by ImmunoPET imaging. The project involves the manufacturing of TF12 that will be used to assess bsMAb stability, immunohistology, and toxicology/PK studies in monkeys. The hapten-peptide to be used in this project is already being produced under GMP conditions at no cost to this application. These studies are required before a IND application can be considered. PUBLIC HEALTH RELEVANCE: This project will develop a new and promising positron-emission tomography (PET) imaging system for the detection of prostate cancer. The procedure is based on a tri-Fab humanized recombinant bispecific antibody that targets the tumor-associated antigen, TROP-2 that is highly expressed in nearly all prostate cancer specimens. The bsMAb is used in a pretargeting setting with an 18F-labeled hapten-peptide using a novel procedure for preparing the labeled product. This procedure has been shown to be more sensitive and specific than 18F-FDG for detecting cancer.